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What is an optimal diet?

Michael Cala interviews nutrition expert and cancer-prevention specialist Moshe Shike, M.D. about what constitutes a healthy diet.

Discovery Health: With all the contradictory dietary information on the market, what do you feel is an "optimal" diet?

Dr. Shike: The best diet for health maintenance, and for the prevention of avoidable diseases, should include a wide variety of foods from the four food groups. Such a diet should conform to the best knowledge we have based on good science and not on clever marketing. A healthy diet should both induce weight loss in the obese, and help all individuals prevent nutrition-related diseases such as heart disease, diabetes, cancer and others.

In terms of actual food composition, an optimal daily diet would include an appropriate amount of calories. These caloric sources should include 20 percent fat, 20 percent protein and 60 percent carbohydrates.

A healthy diet should routinely include at least nine servings daily of fruits and vegetables, and should contain both soluble and insoluble fiber.

Discovery Health: That seems to be the diet many people try to follow.

Dr. Shike: Yes, but only a few succeed in shedding excess weight. A critical and often overlooked part of designing a good diet is determining the daily calorie intake that each person requires. It is definitely not a "one size fits all" approach.

Discovery Health: Would optimal calorie requirements be calculated by height and weight, or by some other measure?

Dr. Shike: The number of calories required each day is determined principally by body size, by level of daily physical activity and body weight goals. Diets are developed by determining how many calories a person typically needs to have enough energy to complete routine tasks: living, working and playing.

People who have jobs requiring low or moderate physical activity, and who have an average-sized body, should consume somewhere in the neighborhood of 1,800 calories a day.

In terms of the 20-20-60 recommendation, someone striving for optimal daily calorie intake would consume 40 grams (360 calories) of fat, 90 grams (360 calories) of protein, and 270 grams (1,080 calories) of carbohydrates. That's an approximation, of course. But it would be enough to provide energy and maintain current weight in a person with low to moderate physical activity.

On the other hand, someone who performs strenuous physical activity on a daily basis would need more calories to maintain present weight.

Discovery Health: What is the best way to accurately determine daily calorie requirements? Is this a do-it-yourself project?

Dr. Shike: The first step is to consult a registered dietitian, who will evaluate your nutritional requirements based on height, weight and level of daily physical activity.

Typically, an interview will include a full nutritional and health history, height and weight and determination of Body Mass Index, or BMI. This is a number arrived at by using a formula that factors in height and weight. The number derived indicates whether the person is overweight or not. From this, calorie requirements are calculated, and a diet is designed with an appropriate mixture of fat, protein and carbohydrates.